On May 20, 17-year-old Zach Sobiech passed away after a long battle with osteosarcoma. But before he died, the aspiring musician created a heartfelt and uplifting song about his struggle, titled “ Clouds,” that has been heard by millions.

“You can either sit in your basement and wait. Or you can get out there and do some crazy stuff,” Sobiech said months before his death. “My closure is being able to get my feelings into these songs.”

Before his death, Sobiech and his family set up a donations page where people could contribute funds to children’s cancer research. KS95 put Thursday’s event together and says all proceeds from the video will go to Zach’s charity.

Needless to say, the video is spectacular, shifting from multiple levels inside the mall, as the 5,000 individuals create entirely new soundscapes in harmony with Zach’s original recording.

He wrote the song as a sort of goodbye to his family and friends. Here is sample of the lyrics:

We could go up, up, up And take that little ride And sit there holding hands And everything would be just right And maybe someday I'll see you again We'll float up in the clouds and we'll never see the end

If you’re not familiar with Zach’s story, it's worth taking 30 minutes to find out about it. We suggest the following:

First, watch “My Last Days,” a 22-minute video that introduces you to Zach, his family and friends, and how the seemingly always smiling teen planned out the rest of his life.

Then, watch the video of “Clouds." If you haven’t teared up by this point, you may want to seek professional help.

“There’s going to be nobody like him to make music with again and that’s going to be really hard,” explains Zach’s friend and writing partner, Sammy.

But as his family and friends explain, it’s hard to not walk away from his story feeling at least a little bit inspired.

"I think that's actually one of the blessings of cancer is that you kind of come out of denial," his mother explained. "And so in doing that things are better. That life is richer. Everything means more. Beauty is more beautiful.

"He's a beautiful person," she continued, "and I'm so happy to have been Zach Sobiech's mom."